Device for alignment of two substrates

ABSTRACT

A device and method for alignment of a first contact surface of a first substrate with a second contact surface of a second substrate which can be held on a second platform includes first X-Y positions of first alignment keys located along the first contact surface, and second X-Y positions of second alignment keys which correspond to the first alignment keys and which are located along the second contact surface. The first contact surface can be aligned based on the first X-Y positions in the first alignment position and the second contact surface can be aligned based on the second X-Y positions in the second alignment position.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/194,652, filed Jun. 28, 2016, which is a continuation of U.S.application Ser. No. 13/497,602, now U.S. Pat. No. 9,576,825, filed Mar.22, 2012, which is a U.S. National Stage Application of InternationalApplication No. PCT/EP2010/005243, filed Aug. 26, 2010, which claimspriority from European Patent Application No. 09012023.9, filed Sep. 22,2009, said patent applications hereby fully incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to a device for alignment of the first contactsurface of a first substrate with a second contact surface of a secondsubstrate and a corresponding method.

BACKGROUND OF THE INVENTION

Various procedures are known for mutual arrangement and alignment of thecontact surfaces of two substrates, for example wafers, especiallynontransparent wafers.

One known procedure is the use of two pairs of microscopes which areeach calibrated to a certain viewing point. For purposes of alignment,first the lower wafer is moved to under the upper microscopes and themicroscopes are aligned to the lower wafer, the position is fixed andthe two alignment keys of the wafers are stored. Then the upper wafer isaligned to the stored alignment keys using the lower microscopes. Thenthe lower wafer is moved into its original position and the wafers arecontacted. With the above described method high precision can beachieved in the positioning. The system however works only based on thedetected relative positions of the two alignment keys on both wafers toone another so that calibration of the microscopes to one another andthe movement of the wafers in alignment can lead to errors in alignment.Furthermore the number of measurement points on the wafer is limited.The above described method is described in U.S. Pat. No. 6,214,692.

Another approach is to arrange two pairs of microscopes between thewafers to be contacted in order to align the two alignment keys oppositeone another, then to move the microscopes out and to finally move thewafers exactly onto one another. In this connection the correspondingerrors can occur by the relative motion of the wafers to one another andthe relative detection of the alignment keys.

The alignment accuracy of the known alignment technologies is in theregion of 0.5 μm, the distribution of the structures which are locatedon the wafers and which can be aligned to one another, for examplechips, and possible deviations of the chips from the given or nominalpositions on the wafer not being considered so far. The growing interestin 3D integration reduces the spacing and size of the bore holes so thatthere is a great demand for more accurate alignment. The deviation fromthe nominal position of the alignment structures has been ignored todate since the adjustment accuracy which has been possible to date wasfar more than 10 times these deviations. The deviations are generallyless than 100 nm.

One major problem of the existing approaches is the mechanical accuracyof the movements of the components toward one another.

Another problem consists in the optical detection accuracy based on therequired working distance of the optics from the wafers. In typicalalignment devices (for example U.S. Pat. No. 6,214,692) the workingdistance must be large enough to be able to move the holding devices forthe substrates between the optics. The necessity of this distance limitsthe maximum usable magnification of these microscopes and thus themaximum attainable detection accuracy for the alignment keys andsubsequently the alignment accuracy.

In an arrangement of the optics between the wafers, the orthogonalalignment of the optics to the contact surfaces of the wafer is anotheraspect which leads to faults in the micron or nanometer range.

SUMMARY OF THE INVENTION

Therefore the object of this invention is to improve a generic device ora generic method such that higher alignment accuracy which relatesespecially to the entire surface of the wafer is achieved and scrapfactors are minimized with respect to the alignment accuracy. Inaddition, the object of this invention is to increase the throughput inthe alignment of wafers.

This object is achieved with the features of the independent claims(s).Advantageous developments of the invention are given in the dependentclaims. The framework of the invention also includes all combinations ofat least two features given in the specification, the claims and/or thefigures. For the indicated value ranges, values which lie within theindicated limits will be disclosed as boundary values and will be ableto be claimed in any combination.

The object of the invention is to devise a device and a method in whichthe X-Y positions of the alignment keys of two substrates which are tobe aligned can be detected or measured in at least one X-Y coordinatesystem which is independent of the movement of the substrates so thatthe alignment keys of the first substrate can be aligned by correlationof the pertinent alignment keys of the second substrate into thecorresponding alignment positions. With this device and this methodalignment accuracies of <0.25 μm, especially <0.15 μm, preferably <0.1μm, can be implemented.

In other words: The device makes available means for detecting themovement of the substrates, especially solely in the X and Y direction,which are referenced to at least one fixed, especially stationaryreference point and which thus enable exact alignment of thecorresponding alignment keys at least in the X and Y direction.

This is enabled especially in that in addition to the detection meansfor detecting the X-Y positions of the alignment keys there are separateposition detection means for detecting the position of the substrates,especially the position of the platforms which hold the substratesfixed. Position detection means can be laser interferometers and/orlinear motors for movement of the platforms in the X and Y direction.

The X-Y positions of the alignment keys on the first substrate aretransmitted by first detection means to the assigned first X-Ycoordinate system and especially at the same time the X-Y positions ofthe alignment keys on the second substrate are transmitted by seconddetection means to the assigned second X-Y coordinate system which isidentical especially to the first X-Y coordinate system. In thisdetection position the X-Y position of the first substrate is detectedby position detection means for especially indirect detection of theposition of the first substrate, and especially at the same time the X-Yposition of the second substrate is detected by position detection meansfor especially indirect detection of the position of the secondsubstrate.

To the extent the movement of one of the substrates is necessary, forexample for alignment or positioning, this is effected by inherentlyknown driving means which are more accurate than the attainablealignment accuracy for example by linear motors at least by a factor of5, especially a factor of 10, preferably a factor of 50. The drivingmeans can at the same time be used as position detection means. Thus theX-Y positions of the substrates are known. The positions of thereceiving means and/or platforms which hold the substrates fixed can beeven more preferably detected by position detection means which are moreaccurate at least by a factor of 10, especially a factor of 50,preferably a factor of 100, for example laser interferometers, in orderto further minimize errors in positioning.

The position of the respective detection means in relation to or on therespective receiving means or platform is fixed or can be at leastaccurately measured, especially with accuracy which is higher at leastby a factor of 10, especially a factor of 20, preferably a factor of 50than the alignment accuracy.

It is especially advantageous here that more than two alignment keys canbe measured on each substrate since one skilled in the art had notconsidered the use of more than two alignment marks for lack ofimprovement of the alignment result by this measure based on thepreviously required working distance in the detection of the calibrationmarks. The measurement of at least three alignment keys for thealignment of wafers can be considered an independent inventive idea,especially in a combination of any features of this invention.

Furthermore it is possible by the above described configuration to usethe structures, especially chips, which are located on the substrate asalignment keys so that separately applied calibration marks which hadpreviously been necessary for alignment can be omitted. This inventionmakes it possible based on high detection accuracy and flexibility ofchoice of the alignment keys to also use existing marks for example fromlithography, especially stepper alignment marks which are located on thecorners of the exposure fields.

Moreover the device as claimed in the invention and the method asclaimed in the invention can be made adaptive or self-teaching bycalibration or optimization of the alignment of the next substratepairing by measurement of the alignment result and comparison with thecomputed or nominal result. This feature can also be regarded as anindependent inventive idea especially in the combination of any featuresof this invention.

The coordinate origin for the purposes of the invention can be anydefined point of the respective coordinate system. Substrates for thepurposes of this invention are very thin and relative thereto,large-area substrates, especially wafers.

The contact surface is the surfaces of the substrates to be aligned andcontacted, which surfaces correspond to one another, the contact surfacenot necessarily forming a closed surface, but it also can be formed bythe corresponding structures, especially chips or topographies.

In one general embodiment of the invention the device therefore has thefollowing features:

-   -   first X-Y positions of first alignment keys located along the        first contact surface can be detected by first detection means        in the first X-Y plane in a first X-Y coordinate system which is        independent of the motion of the first substrate,    -   second X-Y positions of second alignment keys which correspond        to the first alignment keys and which are located along the        second contact surface can be detected by second detection means        in a second X-Y plane which is parallel to the first X-Y plane        in a second X-Y coordinate system which is independent of the        motion of the second substrate,    -   the first contact surface can be aligned based on the first X-Y        positions in the first alignment position and the second contact        surface can be aligned based on the second X-Y positions in the        second alignment position.

The method as claimed in the invention in a general embodiment has thefollowing steps:

-   -   arrangement of the first contact surface in the first X-Y plane        and the second contact surface in the second X-Y plane which is        parallel to the first X-Y plane,    -   detection of X-Y positions of first alignment keys located along        the first contact surface in the first X-Y coordinate system        which is independent of the motion of the first substrate by        first detection means and detection of X-Y positions of second        alignment keys which correspond to the first alignment keys and        which are located along the second contact surface in a second        X-Y coordinate system independent of the motion of the second        substrate by second detection means,    -   alignment of the first contact surface in the first alignment        position determined on the basis of the first X-Y positions and        alignment of the second contact surface in the second alignment        position which is determined based on the second X-Y positions        and which lies opposite the first contact surface.

The X, Y and Z plane or X, Y and Z direction are advantageously eachaligned orthogonally to one another in order to facilitate thecomputation of the X-Y positions in the X-Y coordinate systems.Advantageously they are identical, especially Cartesian coordinatesystems, preferably with the same scaling.

In one advantageous configuration of the invention it is provided thatfirst X-Y positions of more than two first alignment keys can bedetected and aligned with corresponding second alignment keys. With aplurality of alignment keys the alignment accuracy is further increased,especially when the X-Y positions of each of the respective alignmentkeys are known in particular and as a result of the known X-Y positionsto one another, alignment is possible with a minimum overall deviationof the sum of the especially quadratic deviations of each alignment keyor one corresponding alignment position at a time can be computed foreach substrate.

By the first and second X-Y plane in the detection of the first andsecond X-Y positions being identical, especially in addition at leastquasi-identical, preferably identical, to the contacting plane of thefirst and second contact surface during contacting, the faultsusceptibility in contacting in the Z direction is minimized orprecluded. Identical is defined as a deviation of a maximum of 20 μm,especially 10 μm, preferably 5 μm which also applies to a possibledeviation of the parallelism of the contact surfaces to one another andto the respective platforms or the receiving means.

To the extent the first and/or the second X-Y coordinate system areassigned to the base of the device which is made advantageouslystationary and/or rigid and/or solid, this enables a reliable processwhich is independent of ambient influences.

Since the offset of each first alignment key to the corresponding secondalignment key can be determined in the X-Y direction, the individualdeviation can be considered in contacting. In this way the productionscrap is greatly minimized or the yield is greatly increased, by whichthe production costs are reduced and the production speed is increased.

Another advantage arises in one configuration of the invention from thefact that the first and/or the second detection means during detectionand/or alignment and/or contacting can be fixed, especiallymechanically, preferably on the base. This is because by precludingmotion of the detection means relative to the assigned X-Y coordinatesystem further error sources are eliminated.

In the device as claimed in the invention it is advantageously providedthat the device can be calibrated by test means for checking thealignment of the contacted substrates. The test means enable conclusionsregarding the alignment quality and differences for the computedalignment. The device can therefore be made adaptive and can beself-calibrated. Testing can also take place in an external measurementmeans, the test means within the device yielding the advantage thatpossible problems can be detected early and the corresponding measurescan be taken.

For testing purposes, especially IR transparent test markings which areprovided on the substrates and which enable high-precision determinationof the deviation of the substrates can be used.

It contributes to further error minimization that the first detectionmeans in one advantageous embodiment of the invention are formed by asingle first alignment key detector and/or the second detection meansare formed by a single second alignment key detector.

Exact parallel alignment of the contact surfaces to one another isenabled by first and second distance measurement means and actuatorswhich work especially without contact for movement of the substratestransversely to the X-Y planes being provided for parallel alignment ofthe first and second contact surfaces. Furthermore, providing distancemeasurement means enables detection of cambers of the substrates.

The alignment of the substrates using the exact position information ofthe alignment keys allows computation of the individual alignment of thesubstrate by means of mathematical models which take into accountapplication-specific criteria and/or parameters. Optimization ofalignment can take place especially to achieve maximum yield.

Other advantages, features and details of the invention will becomeapparent from the following description of preferred exemplaryembodiments and using the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a schematic of a top view of the device as claimed in theinvention after loading and rough alignment of the substrates,

FIG. 1b shows a schematic sectional view according to cutting line A-Afrom FIG. 1,

FIG. 2a shows a schematic top view of the device with wedge errorcompensation,

FIG. 2b shows a schematic of a side view according to cutting line A-Afrom FIG. 2a at the start of the wedge error compensation step,

FIG. 2c shows a schematic of a side view according to cutting line A-Afrom FIG. 2a at the end of the wedge error compensation step,

FIG. 2d shows a detailed schematic for the wedge error compensationstep,

FIG. 3a shows a schematic top view of the device as claimed in theinvention in the alignment key detection step,

FIG. 3b shows a schematic detailed view for alignment key detection,

FIG. 4a shows a schematic top view of the device as claimed in theinvention in the alignment of the substrates,

FIG. 4b shows a schematic sectional view according to cutting line A-Afrom FIG. 4 a,

FIG. 4c shows a schematic top view of the device as claimed in theinvention in the alignment of the substrates,

FIG. 4d shows a schematic top view of the device as claimed in theinvention after alignment,

FIG. 4e shows a schematic sectional view according to cutting line A-Afrom FIG. 4 d,

FIG. 5a shows a schematic top view of the device as claimed in theinvention in the alignment checking step,

FIG. 5b shows a schematic sectional view according to cutting line A-Afrom FIG. 5 a,

FIG. 6a shows a top view of one alternative embodiment of the device asclaimed in the invention after loading and rough alignment of thesubstrates,

FIG. 6b shows a schematic sectional view according to cutting line A-Afrom FIG. 6 a,

FIG. 7a shows a schematic top view of an alternative embodiment in thewedge error compensation step,

FIG. 7b shows a schematic sectional view according to cutting line A-Afrom FIG. 7 a,

FIG. 7c shows a schematic top view of the embodiment as claimed in theinvention in the wedge error compensation step,

FIG. 7d shows a schematic sectional view according to cutting line A-Afrom FIG. 7 c,

FIG. 7e shows a detailed view for the wedge error compensation step,

FIGS. 8a and 8b show a schematic top view of the alternative embodimentin alignment key detection,

FIG. 8c shows a schematic detailed view of alignment key detection,

FIG. 9a shows a schematic of an alternative embodiment in the alignmentof the substrates,

FIG. 9b shows a schematic sectional view according to cutting line A-Afrom FIG. 9 a,

FIG. 9c shows a schematic section of the alternative embodiment aftercontacting in the Z direction,

FIG. 10a shows a schematic top view of the alternative embodiment in thealignment checking step, and

FIG. 10b shows a schematic sectional view according to cutting line A-Afrom FIG. 10 a.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a and 1b show a base 9 on which a first platform 10 and a secondplatform 20 are movably accommodated, especially by air supporting. Thebase 9 is advantageously formed from a stationary and/or solid and/orrigid material, especially granite. The movement of the first and secondplatform 10, 20, especially exclusively in the X and Y direction, cantake place by drive means, especially linear motors which are located onthe outer contour of the base 9. Each of the first and second platforms10, 20 is assigned its own drive unit.

The drive unit is connected in a stable, nonflexible manner to the firstor second platform 10, 20 assigned to it in order to transmit the driveforces without error and in a high precision manner to the first orsecond platform 10, 20. The drive units have a maximum deviation of <25nm, especially <15 nm, preferably <5 nm.

A first substrate 1, especially a wafer, is held and fixed flat,especially by a vacuum, on the first platform 10.

A second substrate 2, especially likewise a wafer, can be held and fixedon the second platform 20.

The two substrates 1, 2 are loaded in a loading step by a loading meanswhich is not shown, especially robot arms, onto the two platforms 10,20. The first substrate 1 has a first contact surface 1 k facing awayfrom the first platform 10 for contacting of a second contact surface 2k of the second substrate 2 facing away from the second platform 20.

The substrates 1, 2 are accommodated respectively on the platforms 10,20 by suitable receiving means 12, 22, for example chucks. Temporaryfixing of the substrates 1, 2 takes place by suitable fixing means,especially by a vacuum. The substrates 1, 2 are thus stationary withreference to the platforms 10, 20.

To move the receiving means 12, 22 in the Z direction, especially alsofor compensation of a wedge error, three actuators 11 are arranged onthe side of the receiving means 12 facing away from the first substrate1 distributed over the surface of the receiving means 12. This appliesanalogously to the actuators 21 for movement of the receiving means 22in the Z-direction, especially for the wedge error compensation stepwhich is described below.

When the substrates 1, 2 are placed on the receiving means 12, 22 roughalignment takes place by first and second microscopes 1001, 2001 so thatthe substrates 1, 2 are held prepositioned on the receiving means 12, 22in the X and Y direction or additionally in the direction of rotation.

The first contact surface 1 k forms the first X-Y plane 5 and the secondcontact surface 2 k forms the second X-Y plane 6 which in thisembodiment roughly coincide at least in the detection of the alignmentkeys. The maximum deviation of the planes, even with respect to theirparallelism, should be less than 20 μm, especially 10 μm, preferably 5μm. Moreover the first X-Y plane 5 and the second X-Y plane 6,especially with the aforementioned maximum deviations, are each parallelto the bearing surface of the base 9. This minimizes or prevents errorsin the movement of the substrates 1, 2 in the Z direction, for examplein the contacting of the substrates

The first detection means 7 assigned to the first platform 10 comprisethe microscope 1001, an alignment key detector 1000, distancemeasurement means 1002 and a test detector 1003. The test detector 1003is used for checking and optionally self-calibration of the device asclaimed in the invention after contacting of substrates 1 and 2.

Second detection means 8 are assigned to the second platform 20 andcomprise an alignment means detector 2000, optical detection means 2001and distance measurement means 2002 for the second substrate 2.

Position detection means 30, 31, 32, 33, 34, 35, especially laserinterferometers, are located and fixed on the periphery or in the regionof the outside contour of the base 9 and are intended for exactdetermination of the position of the first platform 10 and/or of thesecond platform 20.

The position detection means 30, 31, 32, 33, 34, 35 have a detectionaccuracy of <25 nm, especially <5 nm, preferably <1 nm, so that possibleerrors of position detection have more or less no effect on thealignment accuracy, especially since the system can be madeself-calibrating.

FIGS. 2a to 2d show the step of wedge error compensation by wedge errorcompensating means, which step preferably follows the prepositioning ofthe substrates 1, 2. To detect the vertical position of the firstcontact surface 1 k of the first substrate 1 the first platform 10 asshown in FIG. 2a is moved to under the distance detector 1002 and thedistances of several measurement points distributed over the surface ofthe first substrate (see FIG. 2d ) are measured there in order to detectand compensate for a possible wedge error. The process is the same withthe second substrate 2 and the corresponding distance detector 2002.

Then the wedge error is compensated by the corresponding movement of theactuators 11 for the first substrate 1 as shown in FIG. 2b and theactuators 21 for parallel alignment of the second substrate 2 as shownin FIG. 2c . The contact surfaces 1 k and 2 k are then parallel,likewise the X-Y planes 5 and 6 which preferably form a single plane(see FIG. 2c ). The parallelism should have the aforementionedprecision.

In particular, following the wedge error compensation a plurality offirst alignment keys 3.1 to 3.n as shown in FIG. 3b are detected by thealignment key detectors 1000, 2000 which are assigned to the first andsecond platform 10, 20, specifically their X and Y coordinates in afirst X-Y coordinate system of the first platform 10 for the firstalignment keys 3.1 to 3.n and the second X-Y coordinate system of thesecond platform 20 for second alignment keys 4.1 to 4.n.

The first X-Y coordinate system is assigned to the first platform 10 andthus to the first substrate 1 which is fixed on it and the second X-Ycoordinate system is assigned to the second platform 20 and thus to thesecond substrate 2 which is fixed on it so that the X-Y positions of thefirst and second alignment keys 3.1 to 3.n, 4.1 to 4.n can be detectedby moving the first and second substrates 1, 2 in the respective X-Ycoordinate system, since the X-Y coordinate systems are independent ofthe motion of the substrates 1, 2. Advantageously the two are aCartesian coordinate system with identical scaling.

After the step of alignment key detection, accordingly the X-Y positionsof the first and second alignment keys 3.1 to 3.n, 4.1 to 4.n which arereferenced to the base 9 are known as the absolute position within thedevice and they no longer change in relation to the platforms 10, 20during the process.

FIGS. 4a to 4e show the step of exact alignment which follows detectionof the alignment keys 3.1 to 3.n and 4.1 to 4.n and FIG. 4e shows thestep of contacting of the two substrates 1, 2. As shown in FIGS. 4a to4d , the first and second platform 10, 20 are each moved into therespective first and second alignment position which is computed on thebasis of the X-Y positions of the first and second alignment keys 3.1 to3.n, 4.1 to 4.n determined beforehand; this is possible based on theknown X-Y positions of the first and second platforms 10, 20.

In the computation of the alignment position, one alignment position ata time with the smallest possible distance of the respectivelycorresponding first to the respectively corresponding second alignmentkeys 3.1 to 3.n, 4.1 to 4.n can be computed by mathematical adjustmentcomputation of the alignment keys 3.1 to 3.n and 4.1 to 4.n. Forexample, the sum of the distances or the sum of the square distances canbe minimized or other known mathematical models can be used. Inparticular, alignment can be done such that a yield becomes possiblewhich is as high as possible depending on the alignment accuracy.

Before the substrates 1, 2 are moved into the position shown in FIG. 4d, movement as small as possible of at least one of the two substrates 1,2 away from the other in the Z direction is necessary, preferably of thesubstrate 2, by actuators 21, especially by uniform motion of theactuators 21. Possible errors in the movement of the substrates in the Zdirection are compensated since the same motion in the oppositedirection is carried out for contacting as shown in FIG. 4c . This isenabled by the detection of the alignment keys 3.1 to 3.n, 4.1 to 4.n asshown in FIGS. 3a and 3b and/or by the step of wedge error compensationas shown in FIGS. 2a to 2d taking place such that the first and secondX-Y plane 5, 6 and thus the first and second contact surface 1 k, 2 kare located in the same plane.

After contacting as shown in FIG. 4e , the substrates 1 and 2 are fixed,for example by known clamping mechanisms or by bonding.

Following the contacting and fixing of the substrates 1, 2, optionallythe contacting quality is checked, i.e. the alignment of the substrates1, 2 to one another by test detectors 1003, preferably in the form of aninfrared measurement which checks the relative position of thecorresponding test keys or the alignment keys 3.1 to 3.n, 4.1 to 4.n onthe first substrate 1 and the second substrate 2. The result iscomparable to the alignment computed beforehand and based on thecomparison the substrate pair can optionally by qualified as scrapand/or based on the determined information supplied to suitablereworking. Furthermore it is possible to execute the device to beself-teaching by the relation of the first to the second X-Y coordinatesystem being corrected or calibrated.

Then the contacted and fixed substrate pair of the first substrate 1 andsecond substrate 2 can be unloaded from the alignment device, especiallyby loading means which are not shown.

The wedge error compensation means can be made in one alternativeembodiment such that a uniformity map of the contact surfaces 1 k, 2 kof the substrates 1, 2 is computed. At the same time or alternativelythereto, the uniformity, especially flatness, of the contact surfaces 1k, 2 k can be influenced by a plurality of actuators 11, 21 by aflexible surface being provided on the receiving means 12, 22.

Another advantage of the device as claimed in the invention consists inthat during processing of a substrate pair it is possible to start withthe next substrate pair to be processed so that parallel processing isenabled. This greatly increases throughput.

FIGS. 6a to 10b relate to one alternative embodiment in which incontrast to the above described embodiment only one of the two platforms10′, 20′, in the specifically shown case the platform 10′, is mademovable. The advantage of this embodiment lies in the simpler execution,the smaller floor space and the smaller production costs. This isbecause only three drive motors instead of five are required formovement in the above described embodiment, specifically one drive motorfor movement in the X-direction, one for movement in the Y direction andone for rotation. In the above described embodiment, two drive motorsare additionally necessary, specifically one for movement of the secondplatform 20 in the X direction and one for movement of the secondplatform 20 in the Y direction.

Accordingly only three position detection means 31′, 33′ and 35′ insteadof six are required in the above described embodiment.

The progression of the method is similar to the above describedembodiment, the movements of the second platform 20 in the alternativeembodiment with the rigid second platform 20′ being compensated orreplaced by the movement of the second detection-means, specifically thealignment key detector 2000′ and optical detections means 2001′ with thefirst platform 10′.

To the extent the function of individual components described in FIGS.6a to 10b is not explicitly described, this is in accordance with theabove described embodiment as shown in FIGS. 1a to 5b and vice versa.

In FIG. 6a the first substrate 1 is held on the first platform 10′ andthe second substrate 2 is held on the second platform 20′, specificallyon receiving means 12, 22. The positions of the first and secondalignment keys 3.1 to 3.n and 4.1 to 4.n were accordingly roughlypre-aligned by low-resolution optical detection means 1001′, 2001′.

While the second detection means, consisting of the alignment meansdetector 2000′, the optical detection means 2001′ and a distancemeasurement means 2002′, are arranged fixed on the first platform 10′ ina defined position, the first detection means consisting of thealignment key detector 1000′, the optical detection means 1001′, adistance measurement means 1002′ and test detectors 1003′ are located onthe second platform 20′ so that the first and second detection means caneach be located opposite the substrate 1, 2 to be measured at the time.

In the wedge error correction shown in FIGS. 7a to 7e , the firstcontact surface 1 k is moved and measured at different positions asshown in FIG. 7e by moving the first platform 10′ to the distancemeasurement means 1002′ which is located fixed on the second platform20′. Then the distance from the measurement points on the second contactsurface 2 k is measured by movement of the distance measurement means2002′ located on the first platform 10′.

Based on the measured distribution, the first contact surface 1 k andthe second contact surface 2 k can be aligned parallel to one another bythe corresponding movement of the actuators 11 and 21.

The parallel first and second X-Y planes 5, 6 have a minor distance, butare not in the same plane in this embodiment.

Then the first alignment keys 3.1 to 3.n of the first substrate 1 aredetected by means of the alignment key detector 1000′ which is attachedto the second platform 20′, specifically their absolute positions in thefirst X-Y coordinate system. From the detected coordinates a linear ornonlinear mathematical distribution model and/or corresponding modelparameters are computed, as in the embodiment as shown in FIGS. 1a to 5b.

Then the second alignment keys 4.1 to 4.n of the second substrate 2 aredetected by means of the alignment key detector 2000′ which is fixed onthe first platform 10′ and their coordinates are detected in the secondX-Y coordinate system. From the detected coordinates a linear ornonlinear mathematical distribution model and/or model parameters arecomputed or approached accordingly.

The alignment position of the first platform 10′ can be computed toalign the substrates 1 and 2 accordingly from the model parameters orthe mathematical distribution model of the first and second alignmentkeys 3.1 to 3.n and 4.1 to 4.n and the positions known by the positiondetection means 31′, 33′ and 35′, especially laser interferometers, andthe relation of the first platform 10′ to the second platform 20′ andthe known positions of the alignment key detectors 1000′ and 2000′ inthe respective X-Y coordinate system.

After alignment, the substrate 1 is moved into contact with thesubstrate 2 by actuators 11 in the Z direction.

The quality of alignment and contacting of the substrate pair accordingto FIG. 10a and FIG. 10b is determined by the test detectors 1003′ whichare attached to the second platform 20′.

Much greater alignment accuracies are achieved by the above describedembodiments, especially distributed over the contact surfaces 1 k, 2 kand with respect to the individual positions of the alignment keys,especially chips, so that an alignment accuracy of <250 nm, especially<150 nm, preferably <70 nm can be achieved.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1 first substrate-   1 k first contact surface-   2 second substrate-   2 k second contact surface-   3.1 to 3.n first alignment key-   4.1 to 4.n second alignment key-   5 first X-Y plane-   6 second X-Y plane-   7, 7′ first detection means-   8, 8′ second detection means-   9, 9′ base-   10, 10′ first platform-   11 actuators-   12 receiving means-   20, 20′ second platform-   21 actuators-   22 receiving means-   30 position detection means-   31, 31′ position detection means-   32 position detection means-   33, 33′ position detection means-   34 position detection means-   35, 35′ position detection means-   1000, 1000′ alignment key detector-   2000, 2000′ alignment key detector-   1001, 1001′ optical detection means-   2001, 2001′ optical detection means-   1002, 1002′ distance measurement means-   2002, 2002′ distance measurement means-   1003, 1003′ test detectors

Having described the invention, the following is claimed:
 1. A devicefor alignment of a first contact surface of a first substrate with asecond contact surface of a second substrate, said device comprising: afirst platform configured to hold the first substrate; a second platformconfigured to hold the second substrate; first detection meansconfigured to detect first X-Y positions of first alignment keys locatedalong the first contact surface of the first substrate in a first X-Yplane in a first X-Y coordinate system which is independent of motion ofthe first substrate, the first detection means comprising a single firstalignment key detector; second detection means fixed on a base of thefirst platform, the second detection means being configured to detectsecond X-Y positions of second alignment keys which correspond to thefirst alignment keys and which are located along the second contactsurface of the second substrate in a second X-Y plane parallel to thefirst X-Y plane in a second X-Y coordinate system which is independentof motion of the second substrate; and drive means configured to move atleast one of the first platform and the second platform to align thefirst contact surface of the first substrate with the second contactsurface of the second substrate, the drive means being furtherconfigured to align the first contact surface based on the first X-Ypositions in a first alignment position and align the second contactsurface based on the second X-Y positions in a second alignmentposition.
 2. The device as claimed in claim 1, wherein the firstdetection means are further configured to detect the first X-Y positionsof more than two of the first alignment keys, and wherein the drivemeans are further configured to align the first X-Y positions of themore than two of the first alignment keys with corresponding secondalignment keys.
 3. The device as claimed in claim 1, wherein the firstand second X-Y plane in the detection of the first and second X-Ypositions are at least quasi-identical to a contacting plane of thefirst contact surface of the first substrate and the second contactsurface of the second substrate during contacting of the first contactsurface of the first substrate and the second contact surface of thesecond substrate.
 4. The device as claimed in claim 1, wherein the firstand/or second X-Y coordinate systems are assigned to the base of thefirst platform.
 5. The device as claimed in claim 1, wherein the firstdetection means is fixed on the base of the first platform.
 6. Thedevice as claimed in claim 1, further comprising: test means configuredto calibrate the device by checking the alignment of the first contactsurface of the first substrate and the second contact surface of thesecond substrate when in contact with each other.
 7. The device asclaimed in claim 1, wherein the first and the second X-Y coordinatesystem are Cartesian coordinate systems and/or have identical scalingand/or coincide.
 8. The device as claimed in claim 1, wherein the seconddetection means comprises a single second alignment key detector.
 9. Thedevice as claimed in claim 1, further comprising: first and secondmeasurement means and actuators for partially aligning the first andsecond contact surfaces by moving the first and second substratestransversely to the first and second X-Y planes.
 10. A method foraligning a first contact surface of a first substrate with a secondcontact surface of a second substrate, the method comprising: arrangingthe first contact surface of the first substrate in a first X-Y plane,the first substrate being held on a first platform; arranging the secondcontact surface of the second substrate in a second X-Y plane which isparallel to the first X-Y plane, the second substrate being held by asecond platform; detecting, using a first detection means comprising asingle first alignment key detector, first X-Y positions of firstalignment keys located along the first contact surface of the firstsubstrate in a first X-Y coordinate system which is independent ofmotion of the first substrate; detecting, using a second detection meansfixed on a base of the first platform, second X-Y positions of secondalignment keys which correspond to the first alignment keys and whichare located on the second contact surface of the second substrate in asecond X-Y coordinate system independent of motion of the secondsubstrate; and aligning the first contact surface of the first substratewith the second contact surface of the second substrate, the alignmentof the first contact surface of the first substrate being in a firstalignment position and being determined based on the first X-Y positionsand alignment of the second contact surface of the second substrate in asecond alignment position lying opposite the first contact surface ofthe first substrate, the alignment of the second contact of the secondsubstrate being determined based on the second X-Y positions.